Duplex steam motor



L 9 pml 23, W36. G. E. CAMPBELL 037 6g? DUPLEX STEAM MOTOR Filed Aug. 6, 1930 3 Sheets-Sheet l Aprfifl 21, 1936.. G. E, CAMPBELL DUPLEX STEAM MOTOR Filed Aug. 6, 1950 s Sheets-Sheet 2 2&3 7,697

Aprifl 21, was.

s. CAMPBELL DUPLEX STEAM MOTOR Filed Aug. 6; 1950 3 Sheets-Sheet 3 Patented Apr. 21, 1936 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to an improvement in duplex steam motors, and is more particularly directed to the steam end of a direct acting steam pump.

The difference between the steam cylinder for a steam engine and a steam cylinder for a direct acting steam pump is that in a steam engine the live steam ports and the exhaust steam ports may be the same, but if separate ports are used they all enter the bore of the cylinder at the extreme end of the cylinder. The valves are attached tightly onto the valve stems, and reversing gearing is usually employed. In the direct acting steam pump, there is nothing to stop the travel of the piston except a steam cushion formed in each end of the cylinder by locating the exhaust ports where they enter the cylinder bore some distance in from the end of the cylinder.

These pumps are shut down quite frequently and as soon as they stop running the steam begins to condense, and if the valve leaks a little the condensation is considerable, so that considerable water collects in the cylinder. Upon starting up, this water is very objectionable and is the cause of many cylinder heads being broken. Water is not compressible and as it fills the clearance space at the end of the stroke, the piston comes back solid against the cylinder head with great force. In starting up, frequently the whole line is filled with water so that water and not steam is fed directly into the cylinder until the water has all been exhausted from both the pump and the steam line.

After the pump is hot and in operation, steam enters the steam end of the valve at about 450 temperature but the exhaust leaves the cylinder and goes through the center of the valve at about 250. It is apparent that when both the live steam and the exhaust steam enter the same valve chamber at such difierent temperatures, the exhaust steam is continually lowering the temperature of the live steam and thereby reducing the pressure and reducing the efficiency of the p p.

This invention obviates these objections by 10- cating the exhaust valves and exhaust ports at the bottom of the cylinders and the steam valves and steam ports at the top. The exhaust steam temperature does not affect the live incoming steam temperature, and any condensation of the water that occurs in the cylinder will readily drain out through the exhaust valve ports.

The intake and exhaust valves have adjacent ends connected together but the intake valve has a lost motion connection with its stem so nected therewith for controlling the admission of that the exhaust valve opens ahead of the intake valve, thereby permitting the exhaust steam toescape before the live steam is admitted.

In the accompanying drawingsf Fig. 1 is a sectional view through the steam 5 end of a pump;

Fig. 2 is an end elevation thereof;

Fig. 3 is a cross-section, of reduced scale, on line 3+3, of Fig. 1;

Fig. 4 is a detail section of an exhaust port;

Fig. 5 is a diagrammatic view showing the operating parts in intermediate positions, with the exhaust valve open, and the intake valve closed; and

Fig. 6 is a similar view with the parts in the opposite extreme positions from Fig. 1.

The steam end of the pump comprises a pair of parallel steam cylinders I, in which are mounted pistons 2 and 2' connected directly to connecting rods 3 and 3, respectively, which connecting rods operate through a cradle 4, and extend to the usual pump pistons located in the pump end of the duplex steam pump. A steam chest 5is mounted at the top of each cylinder I and communicates with the ends of 25 the cylinder through passageways 6. The passageways 6 are controlled by a piston valve I, which controls the distribution of steam from the live steam intake pipe 8, to the respective passageways 6. A valve stem 9 is slidably mounted in each steam chest 5, and is slidably connected with the piston valve I; the valve stem 9 carries abutments l0 thereon to engage the opposite ends of the piston valve 1 for movement of said valves and to allow movement of the valve stem relative to the valve. I

The pair of valve stems 9, one for each steam chest 5, have their forward ends connected by links H and II with rocker arms I2 and I2, respectively, which are operated from spools I3 and I3 mounted on piston rods 3 and 3, respectively. The connection is such that the piston 2 recip rocates connecting rod 3 to operate rocker arm I2, link II and the valve stem and valve con- 45 steam to the cylinder which encloses piston 2'. The latter piston operates connecting rod 3, rocker arm I2, link II, valve stem 9, and valve 1, to control the admission of steam to the cylinder I, which encloses the piston 2. In this way the piston of one of the duplex cylinders operates the inlet valve of the other cylinder through the cross over connections of the rocker arms.

The outer end of the valve stems 9 extend from the end of the steam chest 5 and are pivotally attached to the ends of rocker-beams I 4 through connections I5. The rocker-beams M are pivoted as at I 6 to rocker-beam stands I! fixed to cylinder heads I8. The lower ends of the rocker beams I 4 have connections I9 pivoted thereto for pivotally connecting said rocker-beams with valve stems 253, which extend through an exhaust steam chest 2|; A piston valve 22 is mounted in each of the exhaust steam chests 2| to control the exhaust passages 23, leading to ports 24 which open into the lower portions of the cylinders I and are spaced inwardly from the opposite ends of said cylinders. The valve chests 2I have an exhaust pipe 25 connected therewith for carrying off exhaust steam.

The operation of valve stems 9 from rocker arms I2 and I2 is substantially the same as used heretofore in duplex steam pumps and as described above. However, valve stems 9 also 0perate exhaust valve stems 20 through rocker beams I4 for proper synchronization of the inlet and exhaust valves. The exhaust valve stems 20 being rigidly fixed to exhaust valves 22, while the intake valves 1 are slidably on the valve stems 9, permits the exhaust valves to open ahead of the intake valves and allows the exhaust steam to escape before the live steam is admitted. At the same time this will close the exhaust valve slightly in advance of the closing of the intake, just sufficient to trap a small amount of steam in the end of the cylinder which cushions the piston, providing a steam cushioned cylinder.

Fig. 1 shows the parts of the motor in one extreme position, while in Fig. 5, they have moved to intermediate positions in that piston 2' is approximately midway of its cylinder so that rocker arm I2 is approximately in an intermediate position, and has moved valve stem 9 sufiiciently to open exhaust valve 22, but intake valve "I is not yet open but is just ready to open upon further movement of valve stem 9. Piston 2 has completed its forward stroke so that rocker arm I2 is at its full stroke position.

In Fig. 6, the piston 2 has not yet moved toward the opposite end of its cylinder but piston 2 has completed its backward stroke, thereby fully opening intake valve 7 to admit steam to the opposite side of piston 2, so that the latter will now move back under the power of the steam, and exhaust valve 22 remains open. In Fig. 6, both of the rocker arms I2 and I2 and their pistons 2' and 2, respectively, are at their full stroke positions. Steam now being admitted to the forward side of piston 2 will move the latter rearwardly to reverse the positions of the intake and exhaust valves for piston 2, which thereby reverses the movement of the latter, as will be understood.

This arrangement materially improves the thermal efficiency of the steam cylinders; it reduces the back pressure in the cylinder and thereby increases the mean effective steam pressure and it facilitates the removal of water from the cylinders and steam line, eliminating to a substantial degree the danger due to confining water in the cylinders.

I claim:

In a duplex motor for a pump, the combination of a pair of cylinders arranged side by side in parallel relation, a piston operatively mounted in each cylinder and having a piston rod connected therewith, a steam chest mounted above the cylinders and communicating with each of the cylinders at the extreme ends thereof, a piston valve slidably mounted in the steam chest above each of the cylinders for controlling the admission of steam thereto, an exhaust steam chest mounted at the bottom of each steam cylinder and communicating therewith at points spaced inwardly from the extreme ends of the cylinder, an exhaust valve operatively mounted in each exhaust steam chest for controlling the/exhaust from the cylinder, a valve steam for each of the piston and exhaust valves, the valve stems for the exhaust valves being fixed thereto and the valve stems for the piston valves having slidable connections therewith for movement of the valve stems relative to the piston valves, a rocker beam pivotally connecting the outer ends of the valve stems for each of the cylinders, means carried at the ends of the cylinders for pivotally supporting the rocker beams, and means operatively connected with the forward end portion of each of the piston valve stems and operatively connected with the connecting rod of the opposite cylinder for operation of the piston valve therefrom.

GEORGE E. CAMPBELL. 

